As with any successful total knee arthroplasty, proper balancing of the knee joint is of the utmost importance. This balancing is achieved primarily through proper distal femoral and proximal tibia resections or cuts, and to a lesser extent, soft tissue release surrounding the joint capsule.
In order to produce accurate distal femoral and proximal tibial cuts, surgeons use various forms of cutting blocks. The cutting blocks, as useful a tool as they are, still need to be properly positioned by the surgeon. Once properly positioned, the cutting block is fixed to the bone so that a cutting guide surface, usually a saw guide surface, is in correct alignment for performing the required bone resection. However, occasionally after the block is fixed to bone, the surgeon realizes that the cutting guide surface needs to be realigned. To do this, the surgeon must remove the block from the bone and re-attach it in the correct position. Thus there has been a need for ways to reposition the cutting guide surface without removing the entire block from the bone.
U.S. Pat. No. 4,703,751 to Pohl, relates to a distal femoral resection guide having two plates, wherein one plate is positioned on the femur surface and the second plate is positioned on the first plate. Rotational movement is allowed between the first and second plates, and the second plate can be fixed to the first plate by a screw.
U.S. Patent Application Publication No. 2002/0198531 to Millard et al., relates to an apparatus for positioning the cutting angle of a bone cutting guide. The cutting guide is fixed to the bone surface upon determination of the proper angle.
U.S. Pat. No. 5,342,367 to Ferrante et al., relates to a cutting guide for ostectomy of the medial and lateral tibial surface during knee surgery.
U.S. Pat. No. 6,090,114 to Matsuno et al., relates to an apparatus for resecting the tibia. Stabilizing pins are placed in the cutting block, upon proper alignment, thereby allowing the proper tibial plateau resection plane to be created.
As mentioned above, the position of the cutting block needs to be determined by the surgeon, and one of the position determinations, in total knee arthroplasty, relates to the varus/valgus angle. Varus refers to rotation inward towards the midline of the body; while, valgus refers to rotation away from the midline of the body. This angle must be determined prior to making the proximal tibial cut, as an improper angle will prevent proper balancing of the knee joint. A cutting block placed on the anterior side of the proximal tibia, would need to be properly positioned according to the varus/valgus angle, i.e., rotated in a clockwise or counterclockwise fashion about an anterior-posterior axis through the proximal tibia.
Typically, when a surgeon positions a proximal tibial cutting block and realizes that the cutting guide surface is incorrectly positioned, i.e., at the wrong varus/valgus angle, he has several options, if a resection has already been made. One option is that a free hand cut with a sagital saw can be made, at, for example, a corrected varus/valgus angle, but this process does not often provide a perfectly accurate cut. Alternatively, the surgeon may simply accept the error and attempt to compensate in some other manner. In another option, the tibial cutting block originally fixed in an incorrect position and utilized to make an original cut, can be repositioned and re-pinned at a new varus/valgus angle. Finally, a correction block having a different varus/valgus angle can be slid over the existing pins used for the original cutting block. However, all of these options create additional work for a surgeon and add time to an already extensive surgery. Therefore, there is a need for a cutting block that can allow for resection at various varus/valgus angles, without having to be repositioned and re-fixed or re-pinned to the bone.